Non so come mettere le variabili
dentro la funzione Calcola()


Totale.value = (parseFloat("0"+antipasti) ....?

<html>

<head>
<meta http-equiv="Content-Type" content="text/html; charset=windows-1252">
<meta name="GENERATOR" content="Microsoft FrontPage 4.0">
<meta name="ProgId" content="FrontPage.Editor.Document">
<title>Nuova pagina 2</title>
<meta name="Microsoft Border" content="tb, default">
</head>
<script>
var antipasti = document.FormMenu.ANTIPASTI;
var valAntipasti = antipasti.options[antipasti.selectedIndex].value;

var primi = document.FormMenu.PRIMI;
var valPrimi = primi.options[PRIMI.selectedIndex].value;

var secondi = document.FormMenu.SECONDI;
var valSecondi = secondi.options[SECONDI.selectedIndex].value;

var invitati = document.FormMenu.INVITATI;
var valInvitati = invitati.options[INVITATI.selectedIndex].value;

//funzione per il calcolo del totale
function calcola(){
with (document.FormMenu){
Totale.value = (parseFloat("0"+ANTIPASTI.value) + parseFloat("0"+PRIMI.value) + parseFloat("0"+SECONDI.value)) * parseFloat("0"+INVITATI.value);
}
}
</script>


<body>
<hr>
<form name="FormMenu">
<div align="center">
<table width="95%">
<tr>
<td width="208" align="center"><font face="Tahoma" size="2" color="#000080">Antipasti</font></td>
<td width="186" align="center"><font face="Tahoma" size="2" color="#000080">Primi</font></td>
<td width="146" align="center"><font face="Tahoma" size="2" color="#000080">Secondi</font></td>
</tr>
<tr>
<td width="208" align="center"><font face="Tahoma" size="2">

<select size="4" name="ANTIPASTI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">misti di salumi e di mare</option>
<option value="5">MISTI DI SALUMI</option>
</select> </font></td>
<td width="186" align="center"><font face="Tahoma" size="2">

<select size="4" name="PRIMI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">CARNE</option>
<option value="5">Crespelle alla valdostana</option>
</select> </font></td>
<td width="146" align="center"><font face="Tahoma" size="2">

<select size="4" name="SECONDI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">CARNE</option>
<option value="5">Filetto al raggio di sole</option>
</select>

</font></td>
</tr>
</table>
<div align="center" style="width: 742; height: 263">

<table width="95%">
<tr>
<td width="208" align="center"><font face="Tahoma" size="2" color="#000080">Contorni</font></td>
<td width="186" align="center"><font face="Tahoma" size="2" color="#000080">Dolci
e formaggi</font></td>
<td width="146" align="center"><font face="Tahoma" size="2" color="#000080">Torta</font></td>
<td width="152" align="center"><font face="Tahoma" size="2" color="#000080">Vini</font></td>
</tr>
<tr>
<td width="208" align="center"><font face="Tahoma" size="2">

<select size="3" name="CONTORNI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">Patate all'agro</option>
<option value="5">Verdure ai ferri</option>
</select> </font></td>
<td width="186" align="center"><font face="Tahoma" size="2">

<select size="3" name="DOLCI_E_FORMAGGI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">Formaggi misti</option>
<option value="5">frutti di bosco con gelato</option>
</select> </font></td>
<td width="146" align="center"><font face="Tahoma" size="2">

<select size="3" name="TORTA" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">Saint'honorè </option>
<option value="5">della casa</option>
</select> </font></td>
<td width="152" align="center"><font face="Tahoma" size="2">
<select size="3" name="VINI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="3" multiple>
<option value="5">Bianco Lugana </option>
<option value="5">Rosso del Garda</option>
</select></font></td>
</tr>
</table>
<div align="center">
<table>
<tr>
<td>
<p align="center"><font face="Tahoma" size="2" color="#000099">Invitati</font>
</td>
</tr>
<tr>
<td>

<font face="Tahoma" size="2"><select size="3" name="INVITATI" style="font-family: Arial; font-size: 10 pt; color: #000080" tabindex="4" multiple>
<option value="50">fino a 50</option>
<option value="70">da 50 a 70</option>
<option value="90">da 70 a 90</option>
<option value="110">da 90 a 110</option>
<option value="130">da 110 a 130</option>
<option value="150">da 130 a 150</option>
<option value="200">da 150 a 200</option>
<option value="250">da 200 a 250</option>
<option value="300">da 250 a 300</option>
<option value="500">oltre 300</option>
</select></font>
</td>
</tr>
</table>
</div>



Per il vostro pranzo è prevista una spesa di
<input type="text" name="Totale" size="15">


<input type="button" value="Totale" name="calcola" ONCLICK="Calcola()">



</div>
</form>


</div>
</body>

</html>